1. Field of the Invention
The invention relates to a hydrodynamic machine, in particular a hydrodynamic retarder to produce a braking torque by way of a fluid.
2. Description of the Related Art
Hydrodynamic machines or hydrodynamic retarders generally include a housing in which a first bladed wheel, in particular a rotor and a second bladed wheel, in particular a stator arranged concentrically thereto which together form a toroidal chamber, and that are grouped about a common axis of rotation are arranged.
Retarders or hydrodynamic brakes can be arranged in a drive train on the motor side or respectively gear box side. The fill level of the retarder with a working fluid, for example oil or water with or without additives, determines the rotor “braking torque”. When operating the retarder, oil for example is pumped into the working chamber. During braking operation, the driven rotor accelerates this oil and transfers it on the outside diameter of the working chamber to the stator. There, the oil is slowed and returned via the inside diameter of the working chamber back into the rotor. Due to the generally known interaction between rotor and stator the braking torque develops.
A hydraulic system ensures that in the non-braking operation and/or in the braking operation the working chamber is supplied or respectively filled with the appropriate working medium. It is thereby of special consideration that the heat that is generated in both operational modes is removed from the working chamber by way of the working medium and is returned for cooling to a cooling circuit in a cooler. It is particularly necessary in the non-braking operation that a minimum volume is routed through the working chamber in order to cool the retarder also in the non-braking operation.
The working chamber is connected to a working fluid circuit via the fluid supply and the fluid discharge, wherein said circuit consists essentially of a working fluid accumulator, a cooler, a pump and several valves. An open loop and closed loop control unit is connected with the components of a hydraulic system in such a manner that the braking torque and/or working medium flow can be controlled or respectively regulated.
A hydraulic system of this type is known for example from DE 10 2006 030 791 A1. In this hydraulic system the objective is essentially to direct the working medium in all operational modes through a cooler in order to achieve optimum temperature control. The working medium is an oil that at the same time is used for gear lubrication. For adaptation of the volume flow it is provided to control the pump of the hydraulic system.
It is the objective of the current invention to suggest an improved hydraulic system for a hydrodynamic machine. In particular, with the objective to improve the electro-hydraulic system in regard to the adjustability of the braking performance.